Complete urinary blockage - changing food habits?

Hi, I'm new here! I found these forums while searching for cat food information and I need your help...

My almost 4 year old cat Pipo was acting strange yesterday, asking for attention and leading me to his litter box to show me nothing was coming out while trying to pee. He even jumped in the bathtub (he hates it) and started scratching the tub while I was in the toilet. I don't know if he thought that that was my "litter box" and was trying to tell me his wasn't working. He tried to pee on the rug too because he was probably thinking that his box was the problem. He was so confused it makes me wanna cry...

My dad left for England 2 days ago so it was just me (I'm 20 but I don't have a drivers license) and my brother, whom I had to convince to take us to the vet. No one was actually taking me serious so it took a lot of convincing, and my dad even told me that it was probably nothing and to just wait. Long story short, we went to the vet and they told us if we had waited 1 more day he could've died and that it was probably crystals.

So now he's there with a catheter and they told me he will have to stay with it for 72 hours, plus another 24 hours to see if he can pee after. They called me today and told me that yes, something was blocking the way because it was hard to get the catheter in, his blood and urine results were fine, his temperature was normal now (it was low when we left him there) but that he wasn't eating anything. I'm hoping everything turns out alright...

So... diet. He always ate Purina Friskies dry food (my dad buys it) and he drinks tons of water. I think it was to compensate for the dry food because it was seriously a lot of water, he had 2 bowls for water refilled every morning, and by dinner they were dry. We had a female persian when I was little and she ate dry food but never had problems, but she's female so there's that.

I started reading about dry food and how wet food is way better so I want to change his diet to mainly wet food. Problem is, my dad is the one that pays for his food and 5kg of dry food is less than 20 euros and lasts for almost 2 months... Not to mention the ~250euros this trip to the animal hospital is going to cost... The vet told me we had to buy Royal Canin Cat Urinary S/O for him but that's dry too and the wet version is too expensive.

I asked the vet from the clinic where we adopted Pipo for an opinion, and told her I was reading other opinions on the internet, and how a wet food only diet seems to be better according to it, but she told me that all her cats are fed mainly dry food and sometimes, as a treat, 3 or 4 times in a week, she'd give them wet food. Of course I will be feeding him the food they recommend for the time needed but I asked her "How about, after stabilizing, feeding him 80% normal wet food 20% dry urinary food? And she told me that the reverse would be better, 80% dry 20% wet.

Now I don't know who to trust. I'm from Portugal and I'm used to people having very fixed mentalities. I don't know if this is a case of that. She mentioned how, some years ago, wet food was said to be terrible for cats and to just feed dry, but that it was changing a bit now and that wet food is "acceptable" now. As a treat. But that's not what I'm reading at all on the internet and I seriously want what's best for my cat.

I've been looking into zooplus and into Animonda, Bozita and Smilla. They're the cheaper ones and accepted in the "cat food list" here. I was thinking about 200g wet food a day and a bit of dry urinary food to complement it, and that would cost around 30 euros a month. I think I can convince my dad that it's for the best and even help him pay for it with the money I save from birthdays and christmas, etc. My cat is big but overweight (7kg), so he needs to lose some weight. He's sterilized, sleeps all day and is an indoor cat, super afraid of going outside, so no stress (I think). He drinks tap water, could that influence his health? A lot of people choose to drink tap water around here because it's pretty ok to drink, I don't think it's a very hard water, probably medium.

I think that's all, sorry for the long text... What do you recommend me to do? (I'm attaching some pics of him too so you see the good boy he is)